javascript - QUnit 测试返回 "TypeError: undefined is not a function"

Question

我有一些示例代码，来自 Glen Johnson 的书使用 JavaScript 和 CSS3 在 HTML5 中编程。

我的“应用代码”如下:

// Demo of how implementing inheritance works

var Vehicle = (function () {
    function Vehicle(year, make, model) {
        this.year = year;
        this.make = make;
        this.model = model;
    }

    Vehicle.prototype.getInfo = function () {
        return this.year + ' ' + this.make + ' ' + this.model;
    };

    Vehicle.prototype.startEngine = function () {
        return 'Vroom';
    };

    return Vehicle;
})();

var Car = (function (parent) {
    Car.prototype = new Vehicle();
    Car.prototype.constructor = Car;

    function Car(year, make, model) {
        this.wheelQuantity = 4;
        parent.call(this, year, make, model);
    }

    Car.prototype.getInfo = function () {
        return 'Vehicle Type: Car ' + parent.prototype.getInfo.call(this);
    };

    return Car;
})(Vehicle);

var Boat = (function (parent) {
    Boat.prototype = new Vehicle();
    Boat.prototype.constructor = Boat;

    function Boat(year, make, model) {
        this.propellerBladeQuality = 3;
        parent.call(this, year, make, model);
    }

    Boat.prototype.getInfo = function() {
        return 'Vehicle Type: Boat' + parent.prototype.getInfo.call(this);
    }
})(Vehicle);

我的测试如下:

module("Implementing Inheritance", {});

test('Creating a Vehicle', function () {
    expect(2);
    var actual,
        expected,
        v = new Vehicle(2012, 'Toyota', 'Rav4');
    actual = v.getInfo();
    expected = '2012 Toyota Rav4';

    equal(expected, actual);

    actual = v.startEngine();
    expected = 'Vroom';
    equal(expected, actual);
});

test('Create a Car', function () {
    expect(5);

    var expectedYear = 2012,
        expectedMake = 'Toyota',
        expectedModel = 'Rav4',
        c = new Car(expectedYear, expectedMake, expectedModel);

    equal(c.year, expectedYear, 'Year');
    equal(c.make, expectedMake, 'Make');
    equal(c.model, expectedModel, 'Model');
    equal(c.wheelQuantity, 4, 'wheelQuality');
    equal(c.getInfo(), 'Vehicle Type: Car ' + expectedYear + ' ' + expectedMake + ' ' + expectedModel, 'getInfo()');
});

test('Create a Boat', function () {
    expect(5);

    var expectedYear = 12334,
        expectedMake = 'dummy-make',
        expectedModel = 'dummy-model',
        expectedPropellerBladeQuality = 3,
        b = new Boat(expectedYear, expectedMake, expectedModel);

    equal(b.year, expectedYear, 'Year');
    equal(b.make, expectedMake, 'Make');
    equal(b.model, expectedModel, 'Model');
    equal(b.propellerBladeQuality, expectedPropellerBladeQuality, 'propellerBladeQuality');
    equal(b.getInfo(), 'Vehicle Type: Boat ' + expectedYear + ' ' + expectedMake + ' ' + expectedModel, 'getInfo()');
});

当它们运行时，创建汽车测试通过，但是创建船测试失败，并出现以下异常:

Died on test #1     at file:///C://JavaScript_Samples/tests/implementingInheritance.js:33:1: undefined is not a function
Source:     
TypeError: undefined is not a function
    at Object.<anonymous> (file:///C:/JavaScript_Samples/tests/implementingInheritance.js:40:13)

我看不出其中的原因，Car 和 Boat 的代码对我来说似乎相同。

我在 Chrome 和 Firefox 中尝试过此操作，结果是相同的。

有什么建议吗？

Answer 1

您缺少创建的 Boat 类的 return 语句:

var Boat = (function (parent) {
    Boat.prototype = new Vehicle();
    Boat.prototype.constructor = Boat;

    function Boat(year, make, model) {
        this.propellerBladeQuality = 3;
        parent.call(this, year, make, model);
    }

    Boat.prototype.getInfo = function() {
        return 'Vehicle Type: Boat' + parent.prototype.getInfo.call(this);
    }

    // insert return statement here
    return Boat;
})(Vehicle);